1. Field of the Invention
The present invention relates generally to an imaging system.
2. Description of the Related Art
There is known imagers for reading codes such as barcodes and characters or symbols and including an image sensor such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). One known type of such imagers is an imager that utilizes an optical system having, due to axial chromatic aberrations, different focus positions for different wavelengths of light to provide a large depth of field, thereby providing a large readable range. An example of such an imager is disclosed in Japanese Laid-open Patent Application No. 2011-078097.
However, such conventional imagers are disadvantageous in that, in a situation where brightness of an object varies depending on the wavelength of light, depth of field cannot be extended effectively. This is because, in such a situation, contrast varies considerably depending on the wavelength of light.
Therefore, there is a need for an imaging system capable of efficiently extending depth of field.